Potent



June 30, 1959 F. L. J. VAN LAMOEN ET AL 2,892,669

DYE: BATH AND PROCESS FOR CONTINUOUS DYEING Filed April 1a, 195e A Y 2,892,669 DYE BATH' PROCESS non CONTINUOUS DYEING Application April 1s,- 1956, serial No. 578,991 claims priority, application Netherlands April zo, 195s 5 claims. (C1. 8&34')

This invention relates to an improvement in vat dye baths and in continuous vat dyeing therefrom,- Whereby a single bath containing both the unreduced vat dye and the reducing agent may be used and the reduction of the vat dye accomplished in a steam chamber adjacent the dye bath.

In dyeing textiles with vat dyes various continuous processes have been used. For instance, in one well known process a vat dye in unreduced or pigment form is applied to a strip of textile material, and the strip is then passed through an alkaline reducing bath. The cloth may be dried before entering the reducing bath, but this is not necessary. ln or after passing through the reducing bath the dye is reduced to the soluble leuco form and fixed on the ber by a heat treatment. The reduction of the pigment into the leuco form may be accomplished in a steam chamber as described for example in U.S. Patent 2,487,197, or by running the wet textile through a heated oil bath or through a molten metal bath. To complete the process the cloth is run through an oxidizing bath, or otherwise oxidized, rinsed, soaped, rerinsed and dried in the customary manner.

yOne of the objections to these known processes is that at the beginning of the dyeing operation no predictable results can be secured making it necessary to pass substantial quantities of the cloth through the dyeing process before stabilized conditions are established with the resulting wastage of the ununiformly dye cloth, so that these processes can only be applied economically to the handling of large quantities of many thousand meters of length wherein the percentage of initial wastage can be kept relatively low. ln these processes it is only after some time that an equilibrium is established between the quantity of the dye carried into the reducing bath with the cloth, and the quantity of dye which, in reduced form, is absorbed from the reducing bath by the libers.

Attempts made heretofore to work continuously with only one bath containing the dye in solution in the leuco form do not give good results. Also in this type of process for xation of the dye on the fiber a steam bath or heated oil may be used for fixation of the dye on the fiber.

It is the object of this invention to provide a dye bath and a process of continuous dyeing therefrom in which the unreduced vat dye in pigment form, together with the reducing agent are applied to the cloth from a single bath and in which no reduction of the dyestuft takes place until the said cloth is heated for example in a steam chamber to approximately 100 C. In this manner stabilized dyeing conditions may be maintained from the start of the dyeing operation and the initial wastage heretofore encountered in continuous dyeing operations completely eliminated.

Various other objects and advantages of the invention will become apparent as this description proceeds.

yIn accordance withthe invention herein described the diilculties of the prior art may be overcome by running a sheet of cellulosic textile material at normal temperature 2,892,669 Patented June 30, 1959 through a bath containing the dye in pigment or unreduced form and containing also as a reducing agent an alkali hydrosulte such as sodium hydrosuliite and stabilized by the presence of a quantity of an aldehyde, as will be described more in detail later on, which bath con# tains also at least l gram molecule of alkali hydroxide per liter. After passing through this bath the usual heating is carriedout, e.g. heating in a steam chamber, to produce quick reduction of the pigment into the leuco form and penetration into and iixation on the iiber. This step is then followed by the usual oxidation of the dye, rinsing), Soaping, rerinsing and drying. The process of this in'- vention will give an even result from the beginning of the dyeing thus enabling one to use a continuous dyeing process on relatively small quantities of goods with no wastage of ununiformly dyed cloth at the beginning of the dyeing process.- v

-It has not heretofore been known that it is possible. to stabilize a bath containing an unreduced vat dye together with at least l gram molecule of alkali hydroxide per liter and a reducing agent such as alkali hydrosuhte, by the addition ofkan aldehyde, thus preventing any reduc# tion of the dye to the leuco form, at room temperatures (that is normally about 20 C.) in' the original dye bath; This invention is based on the discovery that it is possible to prepare a bath containing alkali hydroxide, a reducing agent such as alkali hydrosul'ite, an aldehyde and an unreduced vat dye which bath has an absolute potential which is less negative at normal temperature but is more negative at C. than the value of the leuco-potential of the dye in the concentration used in the dye bath, so that it is possible to produce a bath containing au unreduced vat dye which is completely stable at room temperature and nevertheless the dye may be converted rapidly into the leuco form on the cloth in a steam chamber.

The leuco potential and the bath potential may be measured in the manner described for Vexample in the I. Soc. Dyers and Colorists, vol. 69, pages 583-595 (19753).

As an aldehyde the use of formaldehyde is preferred, but other lower alkanals such as acetaldehyde may be used.

Stable mixtures, containing a vat dye in pigment form, a reducing agent and an aldehyde are known. These known mixtures, however, either contain no alkali hydroxide or only a minor quantity of alkali hydroxide, and contain alkali carbonate and'sometimes amines as triethanol amine or cyclohexyldiethanol amine as the alkaline agents. The reduction of the dye applied on the textile with these mixtures into the leuco form can only be accomplished by a prolonged steam treatment of several minutes, which makes these mixtures unt for use in a continuous dyeing process.

According to this invention by replacing the carbonates or amines of these prior known mixtures with an alkali hydroxide, the time required for the reduction of the dye and xation on the fiber by a steam treatment is much shorter. The time for the steam treatment with the process of this invention depends on the composition of the bath and may vary between 20 seconds andv 2.5l minutes.

The process of this invention is characterized by the fact that a vat dye in pigment form, an alkali hydroxide andan alkali hydrosuliite are applied to cellulosic textile material from a bath stabilized at normal temperatures by the presence of an aldehyde and the dye is later reduced and fixed on the fiber at a temperature of about 100 C. (i.e. in a steam chamber) and then oxidized. In this process the bath should contain at least one gram molecule of alkali hydroxide per liter and a suicient quantity of the aldehyde that the absolute potential of the bath, at the application temperature is less negative than the leuco potential of the dye and at 100 C. is more negative than the leuco potential of the dye at the concentration used in the dye bath.

Very favorable results are secured by using anthraquinone dyes, with which it is possible tot prepare a bath, stable at normal temperature, and in which the dye is reduced to the leuco form in a steam chamber very rapidly. However, in general all dyes of the quinonoid series as well as sulfur dyestuffs may be used.

' The time required for the steam treatment depends on the particle size of the dye. The time mentioned hereinbefore of 20 seconds to 21/2 minutes applies to dyes of the particle size known as Plv. f. f. F. (Pulverfein fr Far- If formaldehyde is used as the aldehyde in preparing the bath, addition of formaldehyde and alkali hydroxide to a bath containing no hydrosulte has to be avoided owing to the possibility of a Cannizzaro reaction.v In any case the pigment is added to such a mixture in such a way that it is not reduced at normal bath temperature. Usually the pigment is the component which is added last to the dye bath.

Any alkali hydroxide and any alkali hydrosullite may be used and the hydrosulte may be replaced by sulfoxylate (rongalite) together with the required excess of formaldehyde.

The requirement regarding the potential of the bath is important in establishing conditions in which the change in the bath potential in going from normal temperature to 100 C. is much greater than the change in the leuco potential of the dye.

Measured with a platinum electrode, the bath potential at normal temperature attains a constant value about half an hour after the bath is prepared.

The accompanying drawings show the dilerence in the bath potential at 20 C. and 100 C. with different concentrations of alkali hydroxide and aldehyde.

In the drawings of each of Figs. 1 to 4 the dye bath contained 80 g. Na2S2O4 per liter. In Fig. l the quantity of formaldehyde is 35 cm.s of formalin (40% by weight) per liter; in Fig. 2 the quantity of formalin is 52.5 cm.3 per liter; in Fig. 3, 70 cm3 per liter and in Fig. 4, 87.5 cm.s per liter. In all of the iigures the unbroken line indicates the potential of a bath which contains an alkaline agent such as 53 g. of NaZCOs per liter; the dotted lines indicates the potential of baths containing l gram molecule (40 g.) NaOH per liter and the dash lines, the potential of baths containing 2 gram molecules of NaOH per liter.

As is shown by the graphs of Figs. l to 4 vat dyes having a leuco potential of between -900 and -`ll millivolts, in the concentrations used, can be successfully applied according to the process of this invention from single baths in which the bath potential is less negative than the leuco potential of the dye at the bath temperature and more negative than the leuco potential of the dye at elevated temperatures of the order of 100 C. Therefore baths containing sodium carbonate are unsuitable because the potential of the bath at 100 C. is still less negative than the leuco potential of the vat dye whereas baths containing sodium hydroxide (or other alkali hydroxides) in amounts of l to 2 gram molecules per liter are suitable, as the bath potential at normal temperature is less negative than the leuco potential of the dye and therefore the dye is not reduced in the bath whereas at elevated temperature the potential of the bath ingredient is more negative than the leuco potential of Y the leuco potential of the dye may be accordingly reduced. These indigoid dyes are however little used in practice because of lack of color fastness.

The colors obtained according to the process of the invention surprisingly show in many cases more brilliancy than the colors obtained with the same dye in a batch vat process.

It is not possible to add reducing substances, as dextrine etc., to the bath for purposes of increasing the viscosity, as these might bring the -bath potential at normal temperatures to a value less than the value of the leuco potential of the dye, and the bath would no longer be stable at normal temperature. All other normal additives which have no influence on the potential of the bath may, however, be used. 7 y

The following examples, which are given for the purpose of illustration and not limitation, show several applications of the process of this invention. f

Example 1 Softened water (0 hardness) was added to make up a volume of 4 liters.

The potential of the bath without the dye was 885 m. volt at 20 C.; immediately after addition of the dye this value amounted to about -790 m. volt.

The leuco potential of the dye is 905 m. volt at a molar concentration of 0.0005. at C.; at the concentration used in the dye bath it was about -1000 m. volt.

A bleached cotton cloth was treated in this bath in such a way that a 3% dyeing was obtainedv(i.e. a 3% increase in dry weight of the cloth). Then the cloth was steamed for 72 seconds, oxidized with a perborate bath, soaped, rinsed and dried.

There was obtained a completely even gray cloth, the color of which was of a deeper shade than the color of a similar cloth dyed with the same dye in a traditional vat.

Example 2 A bath was prepared with the following substances:

100 g. Cibanongelb L.G.R. Plv. if. F. 200 g. glycerol 320 g. sodium hydroxide 320 g. sodium hydrosullite 80% 138 g. formalin (40% by weight) made up to 4 liters with softened water.

' about 100 m. volt lower (that is about -1000 m. volt) the dye, resulting in reduction of the dye and ailixation to the cloth in the steaming process.

Some indigoid dyes are known which have a less negative value for the leuco potential than vat dyes of the quinonoid series. It is possible to use these dyes in a single bath Icontaining less than l gram molecule of alkali hydroxide per liter. When using these dyes according to this invention the amount of alkali hydroxide needed to increase the bath potential at normal temperature above in the concentration used in the bath.

A cotton fabric was padded with this bath so that a dyeing of 2.5% was obtained, and subiected to a steam treatment for about 2% minutes, and afterwards oxidized, soaped, rinsed and dried in the usual way.

This fabric has an even orange-yellowcolor, much more brilliant than the color obtained with the same dye in the usual vat dyeing process.

Example 3 made up to 4.5 liters with softening water.

assesse- The potential of the bath without dye was '910 m. volt; immediately after addition of the dye about -800 m'. volt. The leuco potential of the dye as measured at 60 C. in a molar concentration of about 0.0005 is -800` m. volt, and in the concentration used in the bath it is therefore about -980 m. volt.

A bleached cotton fabric was padded with this bath in such a way that a dyeing of about 4% was obtained, and afterwards 'steam treated for 72 seconds. oxidized with a perborate oxidizing bath, rinsed, soaped and rerinsed in the usual manner. The color obtained showed much higher brilliancy than a similar fabric dyed with the same dye in the vat.

Example 4 A bath was prepared with:

200 g. Caledon dark blue G. Pwd. fine 200 g. glycerol 160 g. sodium hydroxide 320 g. sodium hydrosulflte 80%) 172 g. formalin (40% by Weight) Softened water was added to make a total volume of 4 liters.

The potential of the bath without dye was -910 m. volt; immediately after addition of the dye it was -765 m. volt, whereas the leuco potential of the dye at 60 C. and a molar concentration of about 0.0005 is -810 m. volt, and in the concentration applied in the bath about -900 m. volt.

A cotton cloth was padded with this bath in such a way that a dyeing of 2.5% was obtained and further treated as described in Example 2. This cloth had a completely even blue color.

Example 5 Bath composition:

120 g. Indanthrene Braun R Plv. f.f. F. 200 g. glycerol 160 g. sodium hydroxide 320 g. sodium hydrosulte (80%) 212 g. formalin (40% by weight) Softened water to make up 4 liters.

The potential of the bath without the dye amounted to -890 m. volt; immediately after addition of the dye it was -810 m. volt. The leuco potential of the dye is -860 m. volt at 50 C. and at a molar concentration of about 0.0005.

A cotton fabric Was padded with this bath in such a was that a dyeing of about 3% was obtained; the further treatment was as described in Example 1. The dyed cloth had an even light brown color.

Example 6 The process of the invention may be employed with a mixture of dyes.

A bath was prepared with the following substances:

63 g. Cibanongelb L.G.R. Plv. f.f. F. 63 g. Olive 2 R Plv. f.f. F. 14 g. Indanthrene Grau B. G. Plv. f.f. F. 350 g. glycerol 560 g. sodium hydroxide 241 g. sodium hydrosulte (80%) 241.5 g. formalin (40% by weight) Softened water rwas added until the volume amounted to 7 liters.

A bleached cotton fabric was padded with this bath in such a Way that a dyeing of 2.3% was obtained, followed by a steam treatment of 2.5 minutes. Then the cloth was oxidized, soaped, rinsed and dried in the usual manner. There was obtained an even colored cloth of khaki color of a perfect quality.

It is then d Example 7 Bath components:

120 g. Indanthrene gold orange G. Plv. ff. F.- 200 g. glycerol 160 g. sodium hydroxide 320 g. sodium hydrosuliite 186 g. formalin (40% by weight) Softened water to make up a total volume of 4 liters.

The potential of the bath without dye amounted to -910 m. volt, and immediately after addition of the dye -780 m. volt. The leuco potential of the dye at 60 C. and at a molar concentration of about 0.0005 is 890 m. volt.

A cotton cloth, treated with this bath in the way as described in Example 1, obtains an even and very brilliant orange color.

While our invention is not limited to the use of the above-mentioned dyes, these particular dyes may be further identified from the following publications:

Schulz- Farbstoiftabellen-Erster Ergnzungsband;

F. Weiss- Die Kpenfarbstoife und ihre Verwendung in der Frberei und Zeugdruck-Wien-Springer Verlag-1953;

Colour Index.

The identification of the dyes mentioned in the examples is as follows:

Cibanongelb L.G.R. (which is of Ciba Ltd., Basel, Switzerland.

While several examples of the practice of the process have been given, it will be understood that other methods of practicing the invention and other composition may be used coming within the scope of the following claims.

For example, the bath according to the invention may also be used for batch-wise dyeing. It is also possible to treat textiles comprising cellulosic materials with a bath according to the invention and to carry out the heat treatment after some lapse of time, erg. after some hours.

Since many materials, such as Wool and cellulose acetate are injured by strong alkali, the process according to the invention is restricted to dyeing cellulosic textile materials, by whch are understood materials consisting of unmodified cellulose or of regenerated cellulose.

We claim:

1. Process for the continuous dyeing of cellulose textile fabric in a single bath containing a vat dye in unreduced form, an alkali hydrosulte reducing agent, an alkali hydroxide in the concentration of at least l gram molecule per liter and a lower alkanal, the amount of alkanal in the bath being more than l mol of alkanal per mol of hydrosulfite, the absolute potential of said bath at normal temperature being less negative, but at C. being more negative than the leuco potential of the said dye in the concentration used in said dye bath, wherein said bath is padded on the fabric at a temperature at which the absolute potential of said bath is less negative than the leuco potential of the said dye in the concentration used in said dye bath, followed by reduction of the dye and fixation in the fabric at a temperature of at least 100 C. and oxidation of the dye.

2. A dye bath for continuous dyeing of cellulose textile material which contains an unreduced vat dye, an alkali hydrosulfite reducing agent, an alkali hydroxide in the concentration of at least l gram molecule per liter and a lower alkanal, said alkanal being present in said bath quite new) is a product in an amount greater than one niol of alkanal for every mol of said hydrosulte, the absolute potential of the said dye bath at bath temperature being less negative than the leuco potential of the said dye in the concentration used in said dye bath and the absolute potential of the said dye bath at 100 C. being more negative than the leuco potential of the said dye in the concentration used in said dye bath.

3. The method of dyeing cellulose textile material from a single vat dye bath comprising adding, as dye ingredients, an unreduced vat dye, an alkali hydrosulte reducing agent, an alkali hydroxide in the amount of at least 1 gram molecule per liter and a lower alkanal, said alkanal being present in said bath in an amount greater than one mol ofalkanal for every mol of said hydrosulte, to the dye bath, wherein the absolute potential of the dye bath is less negative than the leuco potential of the dye in said bath at normal bath temperatures, padding cloth with said dye bath ingredients, thereafter heating said padded cloth in a steaming zone whereupon the potential of said dye bath ingredients padded on said cloth becomes more negative than the leuco potential of the dye and the dye is reduced on said cloth, and thereafter oxidizing said dye on said cloth.

4. Process for the dyeing of cellulose' textile material in which a vat dye in pigment form, an alkali hydroxide and an alkali hydrosulte are applied to the fiber, followed by reduction of the dye and fixation in the ber at a temperature of at least 100 C., and oxidation of the dye, characterized in that the textile material is padded with a bath containing the vat dye in pigment form, at least one gram molecule of alkali hydroxide per liter,

an alkali hydrosu'lite reducing agenty and a lower alkanal, said alkanal being present in said bath in an amount greater than one mol of alkanal for every mol of said hydrosulte, so that the absolute potential of the bath at normal temperature less negative than the leuc'o potential of the dye in the concentration in which said dye is present 'in the'bath and at '100 C. the absolute potential of the dye bath ingredients is more negative than the leuco potential of the dye.

5.' A stabilized dye bath for continuous dyeing of cellulose textile material which contains an unreduced vat dye, an alkalil hydrosuliite reducing agent, an alkali hydroxide in the concentration of at least 1 gram molecule per liter and a lower alkanal, said alkanal being present in an amount in excess of one mol of alkanal for every mol of said hydrosulte, said excess alkanal acting to stabilize said vat dye againstV reduction at normal bath temperatures.

References Cited in the le of this patent UNrrED STATES PATENTS 2,447,993 Vieira Aug. 24, 194s 2,487,197 sam et a1. Nov. s, 1949 A FOREIGN PATENTS Great Britain Mar. 28, 1949' OTHER REFERENCES 

1. PROCESS FOR THE CONTINOUS DYEING OF CELLULOSE TEXILE FABRIC IN A SINGLE BATH CONTAINING A VAT DYE IN UNREDUCED FORM, AN ALKALI HYDROSULFITE REDUCING AGENT, AN ALKALI HYDROXIDE IN THE CONCENTRATION OF AT LEAST 1 GRAM MOLECULE PER LITER AND A LOWER ALKANAL, THE AMOUNT OF ALKANAL IN THE BATH BEING MORE THAN 1 MOL OF ALKANAL PER MOL OF HYDROUSULFITE, THE ABSOLUTE POTENTIAL OF SAID BATH AT NORMAL TEMPERATURE BEING LESS NEGATIVE, BUT AT 100* C. BEING MORE NEGATIVE THAN THE LEUCO POTENTIAL OF THE SAID DYE IN THE CONCENTRATION USED INSAID DYE BATH, WHEREIN SAID BATH IS PADDED ON THE FABRIC AT A TEMPERATURE AT WHICH THE ABSOLUTE POTENTIAL OF SAID BATH IS LESS NEGATIVE THAN THE LEUCO POTENTIAL OF SAID DYE IN THE CONCENTRATION USED IN SAID DYE BATH, FOLLOWED BY REDUCTION OF THE DYE AND FIXATION IN THE FABRIC AT A TEMPERATURE OF AT LEAST 100* C. AND OXIDATION OF THE DYE. 